DE102015115282A1 - Method and device for determining an orientation of a sensor unit - Google Patents

Abstract

A method (100) for determining an orientation of a sensor unit (50), wherein the sensor unit (50) comprises at least one acceleration sensor and is installed in a vehicle (70), comprises: detecting (S110) a first sensor signal from the acceleration sensor in an acceleration-free manner Condition of the vehicle (70); Detecting (S120) a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle (70); and determining (S130) the orientation of the sensor unit relative to the vehicle (70) based on the first sensor signal and the second sensor signal.

Description

The present invention relates to a method and an apparatus for detecting an orientation of a sensor unit, and more particularly to a method and apparatus for quickly detecting mounting directions of ESP units.

Electronic Stability Program (ESP) units are driver assistance systems that detect abnormal vehicle conditions and, based on them, cause corresponding backlashes. To perform their function, ESP units typically have at least one yaw rate and one lateral acceleration sensor. These sensors form a sensor unit. In currently conventional ESP units, this sensor unit must be installed with a specific directional orientation in the vehicle. Only then can it function properly and any abnormal lateral accelerations can be clearly distinguished from normal vehicle longitudinal accelerations or braking.

Because of the importance of the ESP, it is therefore necessary to check its installation so as to reliably ensure that the ESP has been used properly and not accidentally upside down.

In order to check the orientation of the sensor unit, a method is used in today's systems in which at least one cornering is required so as to calculate yaw rates of the vehicle from several sensor signals independently. It is checked whether the yaw rates, which are calculated from different input values, agree within certain tolerances and especially in their sign. Such a method is in the document EP 1 118 519 described, wherein according to the described method, the vehicle completes at least one cornering to perform the measurement. This procedure is initially complicated, since a corresponding test track with a sufficient curve must be present. In addition, it carries the risk that in case of incidents an ESP intervention could be required at the very first cornering, even though the ESP has not yet been tested. Finally, a possibly necessary error warning due to the possible wrong mounting position can only be done in or after the first cornering, which distracts the driver from his driving activity. To avoid this, there is a need for alternative ways to reliably inspect an ESP unit in a vehicle.

The object of the present invention is to provide a method and a device for determining an orientation of a sensor unit which do not have the above-mentioned disadvantages and in particular make it possible to carry out low-risk checking of the orientation.

This object is achieved by a method according to claim 1 or claim 4 and by an apparatus according to claim 10. The dependent claims relate to further advantageous embodiments of the subject matters of the independent claims.

In particular, the present invention relates to a first method for determining an orientation of a sensor unit, wherein the sensor unit has at least one acceleration sensor and is installed in a vehicle. The first method comprises the steps of: detecting a first sensor signal from the acceleration sensor in an acceleration-free state (eg, stoppage or rest state) of the vehicle; Detecting a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle; and determining the orientation of the sensor unit relative to the vehicle based on the first sensor signal and the second sensor signal.

The stated order of the steps (also the further steps) does not imply a time sequence or only insofar as it is absolutely necessary. For example, firstly the first sensor signal can be detected and then the second sensor signal (that is to say the acceleration) is detected. However, it can also be accelerated initially and the second sensor signal can be detected, and then the first sensor signal is detected.

An orientation of the sensor unit is understood to mean its spatial orientation with respect to a coordinate system of the vehicle, so that, with known orientation, sensor signals such as an acceleration value in a specific direction unambiguously a vehicle direction (eg a vehicle longitudinal direction, a vertical direction or a vehicle transverse direction) can be assigned. Thus, the sensor unit can be calibrated accordingly, but also a wrong installation can be determined.

The term "detection of sensor signals" is interpreted broadly in the context of the present invention and includes not only the reading of a corresponding sensor signal, but also a query or a simple reception of sensor signals, which are provided for example by a control unit.

The acceleration-free state or the rest state may be generally defined as a state in which only acceleration due to gravity acts on the vehicle, i. H. The vehicle can either stand or move at a constant, straight-line speed or simply roll out.

Linear acceleration may refer to both an increase in speed and a decrease in speed (i.e., braking). Thus, the idle state can be measured in a movement with a constant, nonzero speed, and in a subsequent deceleration the second sensor signal is detected.

Unless otherwise indicated, in the present application, parallel alignment shall also include the case of antiparallel alignment (i.e., non-parallel lines are also not antiparallel).

The above object is achieved by the present invention in that a first sensor signal is used to find or define a vertical direction based on the gravitational acceleration, and the second sensor signal (an acceleration value) during a linear acceleration is utilized about a longitudinal direction of the vehicle to define with the direction of the linear acceleration or to determine a potential rotation about the vertical axis.

The sensor unit may in particular be arranged in or on an ESP unit, so that the orientation of the ESP unit is also known if the sensor unit has been measured accordingly. To calibrate, for example, yaw rate sensors in the ESP unit, no cornering is thus required, since with the determination of the orientation of the sensor unit also an orientation of existing sensors in the ESP unit such as the yaw rate sensor are known. As already stated, the idle state can already be examined before starting the vehicle, so that by simply accelerating the vehicle over a relatively short distance it can already be determined whether the exemplary ESP unit has been installed correctly.

The used acceleration sensor may output sensor signals for a first acceleration axis, a second acceleration axis, and a third acceleration axis, and the vehicle defines a longitudinal axis, a lateral axis, and a vertical axis, wherein the vertical axis is parallel to a gravitational acceleration vector and the longitudinal axis is parallel to the linear acceleration. With these definitions, the step of determining may further include: determining from the first sensor signal a first angle of rotation about the longitudinal axis and a second angle of rotation about the transverse axis. The first angle and the second angle are defined by the associated rotations aligning the gravitational acceleration vector in parallel (or anti-parallel) to the vertical axis.

In addition, storing the adjustment rotation defined by the first angle and the second angle may be included to enable transformation so that sensor signals of the acceleration sensor in the idle state of the vehicle indicate only acceleration along the third acceleration axis. Thus, the acceleration sensor would be calibrated properly.

Of course, the defined transformation does not necessarily have to be executed. Rather, it is sufficient if the corresponding angles are known, so that the corresponding sensor signals detected by the exemplary ESP unit can be interpreted correctly. A possibly oblique installation can be compensated. Likewise, the determined angle can serve only the purpose of warning the driver when a tolerance deviation from an ideal installation on a misplacement is exceeded. Then the installation can be checked.

Determining the orientation by means of the mentioned angles is one possibility. In addition, there are several mathematically equivalent ways to detect a spatial rotation of the sensor unit with respect to the vehicle and to parameterize accordingly, so that the correct installation can be determined or possible inclinations compensated accordingly and the sensor signals can be interpreted correctly.

The acceleration sensor may, for example, be a three-dimensional (3D) sensor and thus detect three independent acceleration values for three axes (directions). The said axes do not necessarily have to be orthogonal to one another, but to be linearly independent of one another. Of course, a 3D acceleration sensor may be constructed by a plurality of independent one-dimensional (1D) and / or two-dimensional (2D) acceleration sensors (which can independently measure one or two accelerations).

In further embodiments, the first method further comprises detecting a motion signal from at least one motion sensor and detecting a vehicle stall (or an acceleration-free state) based on the motion signal.

The present invention also relates to a second method for determining an orientation of a sensor unit of a vehicle, wherein for the vehicle again a longitudinal axis, a transverse axis and a vertical axis is defined.

The vertical axis is parallel to a gravitational acceleration vector, and the sensor unit has at least one acceleration sensor with a predetermined alignment with the vertical axis and is configured to output sensor signals for a first acceleration axis and a second acceleration axis different from the vertical axis. The second method comprises the steps of detecting an acceleration sensor signal (second sensor signal) of the acceleration sensor in response to a linear acceleration of the vehicle along the longitudinal axis, and determining the orientation of the sensor unit in a plane spanned by the longitudinal axis and the transverse axis based on the detected one acceleration sensor signal.

In other embodiments, the methods further include determining from the second sensor signal a third angle of rotation about the third acceleration axis. The third angle is defined by the fact that the associated rotation aligns the linear acceleration of the vehicle parallel or antiparallel to the first axis of acceleration.

Optionally, the methods further include storing the compensation rotation defined by the third angle to enable transformation, such that sensor signals of the acceleration sensor indicate only acceleration along the first acceleration axis at accelerations along the longitudinal axis of the vehicle.

The methods are preferably carried out during a straight-ahead drive (or resting state) of the vehicle. However, this can not always be guaranteed. Thus, the vehicle optionally includes one or more other sensors that detect, directly or indirectly, a rotation of at least one vehicle wheel so as to determine a speed and an acceleration thereof over time. Therefore, the methods may further include the steps of: determining an acceleration value of the vehicle by detecting sensor signals from the another sensor; Determining an amount of linear acceleration based on the second sensor signal; and determining a deviation of the acceleration value from the amount of linear acceleration and taking into account the deviation in the step of determining the orientation.

In further embodiments, the methods also include outputting a warning, if the determined orientation of the sensor unit signals a misincorporation. The misincorporation can be defined as a deviation from a standard condition.

Embodiments also include a storage medium having a computer program stored thereon configured to cause a device to execute one of the previously described methods when running on a processor (processing unit). The storage medium may be a machine-readable medium that includes a mechanism for storing or transferring data in a form readable by a machine (eg, a computer). The device can be, for example, a control unit with a processor on which the computer program runs.

The present invention thus also relates to a device for determining an orientation of a sensor unit, wherein the sensor unit has at least one acceleration sensor and is installed in a vehicle. The device is, for example, the above-mentioned control unit which executes the above-described method and comprises: a detection unit for detecting a first sensor signal from the acceleration sensor in an acceleration-free state of the vehicle and / or a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle. The apparatus further comprises a processing unit for determining the orientation of the sensor unit relative to the vehicle based on the first sensor signal and / or the second sensor signal. The memory unit serves to store the results (eg the determined angle).

In the apparatus, the acceleration sensor may be the aforementioned three-axis acceleration sensor which may have a predetermined attitude to an ESP installed in the vehicle, so that the detected orientation of the sensor unit also indicates the orientation of the ESP. Optionally, the acceleration sensor may also be integrated in the ESP and housed in a common housing together with the ESP.

The present invention also relates to a vehicle having a sensor unit which has at least one acceleration sensor and a device as described above.

The embodiments of the present invention will be better understood from the following detailed description and the accompanying drawings of the different embodiments, which should not be construed as limiting the disclosure to the specific embodiments, but for explanation and understanding only.

1A FIGS. 1 B, B are flowcharts of methods for determining an orientation of a sensor unit according to embodiments of the present invention.

2 shows an apparatus for determining an orientation of a sensor unit according to embodiments of the present invention.

3 shows an exemplary vehicle with built-in sensor unit during vehicle standstill.

4 shows an exemplary orientation of a measured acceleration vector during vehicle standstill.

5 shows the result of a rotation about an x-axis.

6 shows the result of a subsequent rotation about a y-axis.

7 shows the vehicle with a twisted in the xy plane sensor unit.

8th shows the superimposed gravitational acceleration with a vehicle acceleration before compensating for twists.

9 shows the resulting total acceleration after compensating for twists from an upright position.

10 shows the final result after compensation of all twists of the sensor unit.

1A FIGS. 1 B, B are flowcharts of methods for determining an orientation of a sensor unit according to embodiments of the present invention.

1A illustrates a first method for determining an orientation of a sensor unit. The sensor unit has at least one acceleration sensor and is installed in a vehicle. The method comprises the steps of: detecting S110 a first sensor signal from the acceleration sensor in an acceleration-free state of the vehicle; Detecting S120 a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle; and determining S130 the orientation of the sensor unit relative to the vehicle based on the first sensor signal and the second sensor signal.

1B illustrates a second method for determining an orientation of a sensor unit of a vehicle, wherein the vehicle defines a longitudinal axis, a transverse axis and a vertical axis. The vertical axis is parallel to a gravity acceleration vector (assuming the vehicle is upright). The sensor unit comprises at least one acceleration sensor and is designed to Output sensor signals (ie acceleration values) for a first acceleration axis and a second acceleration axis, which are different from the vertical axis z. In contrast to the first method, it is assumed here that the acceleration sensor has a predetermined alignment with the vertical axis. The second method comprises the steps of: detecting S210 an acceleration sensor signal (second sensor signal) of the acceleration sensor in response to a linear acceleration of the vehicle along the longitudinal axis; and determining S220 the orientation of the sensor unit in a plane subtended by the longitudinal and transverse axes of the vehicle based on the detected acceleration sensor signal.

2 shows a device 300 for performing the first and / or the second method, the orientation of a in a vehicle 70 attached sensor unit 50 determine. The device 300 comprises a detection unit 310 , a processing unit 320 and an optional storage unit 330 , The registration unit 310 is configured to receive sensor signals from a sensor unit 50 (eg, an acceleration sensor) and optionally one or more other sensors 80 to recieve. The received sensor signals are sent to the processing unit 320 passed, where an evaluation of the sensor signals.

In the implementation of the first method, the processing unit evaluates 320 two measurements off. In a measurement, an acceleration-free state (eg, idle state) of the vehicle 70 detected and in this state, the gravitational acceleration (in particular their direction) by the acceleration sensor 50 measured (as the first sensor signal). This result is used to detect a possible rotation of the sensor unit 50 from the upright position. This rotation can be defined by transformations (eg, rotations) that determine the gravitational acceleration vector along the vertical axis of the sensor unit 50 align. In a further measurement, during a linear acceleration of the vehicle along the vehicle longitudinal axis, the resulting acceleration (in particular its direction) is determined by the acceleration sensor 50 measured (as a second sensor signal). This result is used to detect a possible rotation of the sensor unit 50 to determine the vertical axis. This rotation corresponds to the rotational transformation that brings the detected linear acceleration vector in the direction of linear acceleration. For example, when the linear acceleration is along the vehicle longitudinal direction without turning, the rotational transformation transforms the measured acceleration vector to point along the vehicle longitudinal axis.

The acceleration sensor 50 For example, a yaw rate and acceleration unit may be packaged in a separate housing and mounted to a vehicle frame. The device may be, for example, an ESP control unit to which the sensor unit 50 is connected and which evaluates the signals and thus early detects a possibly incorrect mounting position of the sensor unit.

The determination of the rotations can thus on the one hand indicate that the sensor unit 50 or the ESP unit 60 wrong in the vehicle 70 was installed. In this case, a corresponding warning message can be issued. However, the determined transformation can also be used to perform a calibration (or calibration) of the sensor unit 50 or the ESP unit 60 to increase the measurement accuracy. In this case, a correction of the installation does not necessarily have to be made. Rather, the deviation from the ideal insertion can be automatically taken into account.

In contrast to conventional methods, this procedure requires only a short acceleration or deceleration distance (for example before or after a short standstill) in order to determine how the sensor unit 50 in the vehicle 70 is installed.

The sensor unit 50 For example, it may be configured as a three-dimensional (or two-dimensional) acceleration sensor (s) and thus to an ESP unit 60 couple that it is in a fixed relationship (ie, orientation) to the exemplary ESP unit. This makes it possible, from the measured acceleration values of the acceleration sensor 50 to an orientation of the ESP unit 60 relative to the vehicle 70 close. Optionally, it is also possible that the three-dimensional acceleration sensor 50 Part of the exemplary ESP unit 60 is or is integrated in this. For example, the ESP unit itself may include one or more acceleration sensors capable of generating sensor signals and determining the accelerations in three mutually different spatial directions. Therefore, the sensor unit 50 be integrated in a control unit such as the ESP unit, so as to automatically determine the correct installation position of the control unit.

The acceleration sensor 50 But not necessarily zwingerderweise a three-dimensional acceleration sensor to be. It may also be configured as a two-dimensional acceleration sensor so that it only detects two independent acceleration values with respect to two independent spatial directions. Such an acceleration sensor is sufficient for the implementation of the second method. In this case, however, it is important that the two-dimensional acceleration sensor 50 such to the exemplary ESP unit 60 coupled, that the two detectable acceleration values are not parallel or antiparallel to the vertical orientation of the vehicle 70 lie, but preferably lie in a plane perpendicular thereto. In this case, however, it is for the calibration of the sensor unit 50 further important that the installation of the exemplary ESP unit 60 or the sensor unit 50 is known or predetermined with respect to the vertical direction, so that only an uncertainty with respect to the rotation around the vertical direction would have to be compensated or determined. The determination of this rotation proceeds in the same way as described in the first method, ie via an acceleration measurement during a linear acceleration of the vehicle and the determination of the direction of the measured acceleration vector.

The other sensor 80 For example, include at least one motion sensor or sensors that detect the engine speed or that detect a rotation of the wheels or their rotational speed. Likewise, sensors may be present which detect a steering angle and thus indicate a cornering. All these additional sensors are coupled, for example via the wheels and speak to appropriate acceleration of the vehicle 70 without relying on the exemplary ESP unit 60 to resort to those independent of these sensors 80 is. Their function will be described in more detail below.

The 3 to 10 show further details of the exemplary procedure for determining the orientation of the sensor unit 50 ,

3 shows first the vehicle 70 from a rear view (left side) as well as from a side view (right side). The coordinate system is selected such that the x-axis extends forwards along the vehicle longitudinal direction, the z-axis represents the vertical direction and the y-axis represents the vehicle transverse direction. In the vehicle is an exemplary sensor unit 50 shown relative to the (global) xyz coordinate system of the vehicle 70 is inclined, ie the own (local) frame of reference of the sensor unit 50 consisting of the (orthogonal) directions a _1s , a _2s , a _3s is rotated with respect to the global xyz coordinate system. For example, the sensor unit 50 relative to the y-axis by an angle φ and inclined relative to the x-axis by an angle θ. The angle φ is also known as roll angle and the angle θ as so-called pitch angle. The choice of axis direction is largely arbitrary, so that in other coordinate systems, one or more of the axes shown in an opposite direction or not at a right angle to each other.

To the inclination of the sensor unit 50 relative to the vehicle 70 is determined, as described above, in a measuring step, the orientation of the gravitational vector g in the unaccelerated state (eg, at a standstill) determined. The following is the standstill of the vehicle in this measuring step, although the present invention is not limited thereto. It is only important that in this measuring step no other, different from gravitational acceleration g acceleration on the vehicle 70 acts.

4 FIG. 10 shows an exemplary orientation of a measured gravitational acceleration vector g during the exemplary vehicle standstill, as in FIG 3 was shown. As the vehicle 70 when stationary, only the gravitational acceleration g acts on the vehicle 70 coming from the sensor unit 50 is measured. In the example shown, the gravitational acceleration g is not aligned along the negative z-axis, but has a value a _s1 in the negative x-axis, a value a _s2 in the negative y-axis, and a value a along the negative z-axis _s3 .

The vehicle standstill shown can be determined, for example, based on a wheel speed using appropriate sensor signals or other vehicle readings (such as from a parking brake, information about an engaged gear or the engine running). For this purpose, the other sensors described above 80 be used. It is also possible to stop the vehicle 70 to detect via ESP sensor signals (rotation rate and other acceleration signals).

When the vehicle is stationary, only the gravitational acceleration g acts on the vehicle by definition 70 such that the following equation applies to the measured acceleration: a _1S ² + a _2S ² + a _3S ² = g ² (1)

To the in the 3 illustrated non-upright orientation of the sensor unit 50 In the following steps, the static roll angle and pitch angle are adjusted in order to be able to take into account accordingly (or to signal a false build). This means that after determining these angles by means of corresponding compensation rotations, the measured acceleration values can first be transformed into a coordinate system in which the gravitational acceleration g acts only in one direction, which can be defined as a vertical direction.

wobei:

This can be done in two steps. In a first step, the measured acceleration vector is first rotated about its x-axis, so that the y-component of the measured acceleration vector disappears. This compensation rotation corresponds to the following transformation:

in which:

5 shows the result of this rotation, ie the rotated acceleration vector g has no component in the y-axis, but only a z-component and an x-component.

wobeiThe next step is the vector of 5 rotated again around the y-axis, so that the resulting vector is perpendicular to the xy plane (ie parallel to the z-axis). The rotation required for this is defined as follows:

in which

6 shows the result of the two turns from the Glgn. (2) to (5), in which the acceleration vector g no longer has x and y components and is oriented parallel to the z-axis.

Maybe the sensor unit 50 but also be rotated by an angle ψ around the z-axis (ie in the xy-plane). The following describes a further procedure, as well as this twist is determined.

7 shows first the vehicle 70 in a plan view, wherein the sensor unit 50 rotated by an angle ψ around the z-axis (ie in the xy-plane). To determine this rotation, the next step is a linear acceleration or straight-line acceleration of the vehicle 70 performed so that the acceleration vector of the vehicle ν. is added to the gravitational acceleration g and provides an overall acceleration vector passing through the sensor unit 50 is detectable.

und dessen momentane Beschleunigung:

Optionally, the instantaneous velocity of the vehicle ν may be determined, for example, from wheel speeds or angular velocities ω ₁ ... ω _n , where n is the number of measurements on different wheels (n ≥ 1). The angular velocities can be measured, for example, with wheel speed sensors (best on non-driven wheels to prevent slippage). If the different wheels diameter r ₁ ... r _n , results for the speed of the vehicle (as an average of the n measurements):

and its instantaneous acceleration:

This acceleration adds vectorially to the previously determined gravitational acceleration g (see 4 ). Assuming that the linear acceleration of the vehicle 70 in the x-direction, ν acts. only in x-direction. The amount of the total acceleration (a1, a2, a3) is thus given by: a ₁ ² + a ₂ ² + a ₃ ² = g ² + ν. ² . (8th)

Since during a movement of the vehicle can not always be completely ruled out that the vehicle drifts sideways or unevenness or inclinations of the vehicle lead to other acceleration values, can optionally be determined based on speeds of the driven wheels, whether the acceleration values actually with the measured values to match.

For this example, the above-described other sensors 80 be used. For example, it can thus be determined from a chronological sequence of additional sensor signals how the speed of the wheels changes in order to determine the acceleration value therefrom. Since this acceleration value is determined from the rotations of the wheels, it detects only speed increase of the vehicle 70 relative to the ground and is not sensitive to deviations from linear acceleration. On the other side, the accelerometer measures 50 the acceleration regardless of the cause of the acceleration, ie it measures a superposition of all accelerations (gravity, vehicle acceleration, cornering, change of the ground, etc.). These other sensors 80 can thus be used effectively to determine further accelerations that can overlap the linear acceleration and distort the result. Therefore, it can also be determined whether the ground is inclined or whether the vehicle is traveling downhill or uphill or laterally inclined. Even unevenness of the ground can be detected, which could also lead to a distortion of the signal.

To achieve this, the accelerometer can be used 50 not only determine the direction of acceleration, but also detects the absolute amount of acceleration. If the vehicle 70 is strictly horizontal and strictly rectilinearly accelerated and if a deviation from the high position has already been taken into account, the absolute value of the acceleration of the acceleration sensor is correct 50 with the acceleration value of the other sensors. If there is a deviation, the measurement conditions were not ideal. The result, ie the detected deviation, can be communicated to a driver, for example, so that he can repeat the test under other conditions. It is also possible to take into account the deviation in the determination of the orientation or to compensate for the additional acceleration, so that the results are not distorted.

8th shows the superimposed vehicle acceleration ν. and the gravitational acceleration g measured in retirement.

9 shows the total acceleration g + ν. as a vectorial addition of the gravitational acceleration g and the vehicle acceleration v., where the known rotations about the x and y axes have already been taken into account (compensated), so that the gravitational acceleration g acts only along the z axis and the effective longitudinal acceleration v. lies in the xy plane.

wobei

(unter den obigen Annahme wäre a_z = 0).Assuming that the linear acceleration ν. of the vehicle 70 defining only an ax acceleration (along the vehicle longitudinal axis), the rotation is given by the following transformation by a twist angle ψ in the xy plane (around the z-axis):

in which

(under the above assumption would be a _z = 0).

10 shows the final result, in which the component ν. is aligned along the x-axis after the normalization made only. Accordingly, the linear acceleration causes effective rotation of the acceleration vector about the y-axis (ie out of the z-axis).

In summary, it is thus possible, the three measured accelerations of the sensor unit 50 in the vehicle acceleration in the vehicle coordinate system (see 2 ) to transform by the following transformation:

The angles φ and θ are determined by the gravitational acceleration g being aligned only along the z-axis, and the angle ψ is defined by the vehicle acceleration ν. has only one component along the x-axis.

From the procedure described so far it follows that for each rotation of the sensor unit 50 relative to the vehicle coordinate system to detect an acceleration by a corresponding sensor signal. Therefore, for a general rotation in all three spatial directions, a three-dimensional or 3-axis sensor signal is required, which can detect both rotations about the pitch angle, about the roll angle and rotations about the vertical axis.

Such a three-dimensional sensor signal may be from a sensor unit 50 which is coupled to the exemplary ESP unit so as to establish an orientation of the ESP unit. However, the ESP unit itself does not need to have a three-dimensional acceleration sensor. In this case, an additional three-dimensional acceleration sensor may be provided which has a fixed orientation with respect to the sensor unit 50 and for calibrating the sensor unit 50 is usable.

However, if neither the sensor unit 50 If a further independent acceleration sensor can detect all three spatial directions, a two-dimensional sensor element can also be used to determine the orientation of the sensor unit 50 determine. However, since not all three spatial directions can be detected when using a two-dimensional sensor unit, it is important for this case that the sensor unit already ensures a vertical installation relative to the vertical axis or has a predetermined angle to the vertical axis.

If this is guaranteed, the steps until the Glg. (5) omitted, since the gravitational vector g is already aligned parallel to the z-axis or due to the fixed angle is correspondingly transformable. In this case, only the steps described by Eqs. (6) to (10) need to be performed.

If the two-dimensional sensor element is not strictly aligned with the z-axis or the vehicle is at a standstill inclined (for example, on a slope), this deviation can be considered as a sensor offset at standstill and adjusted accordingly.

Advantages of embodiments of the present invention and their essential aspects can be summarized as follows.

The present invention enables the orientation of a sensor unit 50 such as an ESP unit 60 to be tested quickly and safely by the procedures described. It is also possible to use the sensor unit 50 or to constantly monitor their orientation (eg, before each journey or even while they are in motion), thus making it possible to relax the rules for accurate installation. Therefore, the procedure described is advantageous for a constant or regular control of the orientation of the sensor unit 50 , By determining the orientation of the sensors, it can be ensured that the ESP is functioning properly.

According to the present invention, accelerations from a sensor unit a ₁ , a ₂ and optionally a ₃ , which are typically oriented orthogonal to each other, are brought into coincidence with the vehicle coordinate system ax, ay, az. Therefore, not only a lateral acceleration sensor is used, but a multi-axis acceleration sensor. If this is a three-dimensional acceleration sensor, the acceleration vector acting on the sensor, including the proportion of gravitational acceleration, can be measured directly. When the vehicle is at a standstill (or a monotonous motion at a constant speed), only the acceleration of gravity acts, so that the position of the sensor unit already before the start of the journey 50 can be determined directly to the longitudinal and transverse axis and a warning can be issued in case of impermissible deviations from the given direction. An incorrect mounting position is thus already detected before or immediately when driving and the driver can be warned in good time. Alternatively, a deviation from the ideal mounting position can be tolerated, with the procedure described serving for calibration (automatically compensating deviations from the ideal position).

A rotation around the high position can be detected by a short acceleration (eg starting). When starting up, for the ESP control unit by the CAN information from the drive and / or the signals of the wheel speed sensors 80 can be seen, is determined by the determined by means of an at least 2D-measuring acceleration sensor change of the acceleration signal, in which angular position about the vertical axis of the sensor unit 50 is mounted.

If the rotation about the vertical axis is known, the transverse acceleration relevant for ESP can be calculated from the magnitude and direction of the acceleration vector, or, if a specific installation direction about the vertical axis is prescribed, a warning is output, if it deviates from the ascertained installation direction.

For this purpose, the actual acceleration in the direction of travel of the vehicle without acceleration components transverse to the direction of travel (cornering) can be measured. This is possible by recognizing by the steering angle sensor that the steering is straight ahead and is detected from signals (eg engine torque and speed, clutch position, engaged gear) from the vehicle communication bus (eg CAN J1939) in that the vehicle is now accelerated from a standing position forward.

Embodiments of the present invention thus allow the ESP unit to be already checked without having to make a turn which may already require ESP intervention. In addition, it is possible that any necessary error warning is already recognized because of a wrong mounting position without having to drive through a first curve.

Possible in the direction of travel or transverse oblique locations of the vehicle must be tolerated within the permitted limits. However, large deviations about the vertical axis can be tolerated by a 2d or 3d acceleration sensor, or specification of the direction of installation about the vertical axis can be dispensed with.

The features of the invention disclosed in the description, the claims and the figures may be essential for the realization of the invention either individually or in any combination.

LIST OF REFERENCE NUMBERS

50

sensor unit

60

ESP unit

70

vehicle

80

additional sensors

300

Device for determining an orientation (control unit)

310

acquisition unit

320

processing unit

330

storage unit

x, y, z

Longitudinal, transverse and vertical axis of the vehicle

a1

first acceleration axis

a2

second acceleration axis

a3

third acceleration axis

G

gravitational acceleration

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1118519 [0004]

Claims (13)

Method for determining an orientation of a sensor unit ( 50 ), wherein the sensor unit ( 50 ) has at least one acceleration sensor and in a vehicle ( 70 ), characterized by - detecting (S110) a first sensor signal from the acceleration sensor in an acceleration-free state of the vehicle ( 70 ); Detecting (S120) a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle ( 70 ); and determining (S130) the orientation of the sensor unit relative to the vehicle ( 70 ) based on the first sensor signal and the second sensor signal. The method of claim 1, wherein the acceleration sensor outputs sensor signals for a first acceleration axis (a1), a second acceleration axis (a2) and a third acceleration axis (a3) and the vehicle ( 70 ) defines a longitudinal axis (x), a transverse axis (y) and a vertical axis (z), wherein the vertical axis (z) is parallel to a gravitational acceleration vector (g) and the longitudinal axis (x) is parallel to the linear acceleration, characterized in that the step (S130) of determining further comprises: determining, from the first sensor signal, a first angle (φ) about the longitudinal axis (x) and a second angle (θ) about the transverse axis (y), the first angle ( φ) and the second angle (θ) define associated rotations that rotate the gravitational acceleration vector (g) parallel or anti-parallel to the vertical axis (a3); and storing the first angle (φ) and the second angle ( 0 ) defined adjustment rotation to allow a transformation, so that sensor signals of the acceleration sensor ( 50 ) in the acceleration-free state of the vehicle ( 70 ) indicate only one acceleration along the third acceleration axis (a3). Method according to claim 1 or claim 2, wherein the vehicle ( 70 ) comprises at least one motion sensor, characterized in that the method further comprises: detecting a motion signal from the at least one motion sensor ( 80 ); and - determining the no-acceleration condition based on the motion signal. Method for determining an orientation of a sensor unit of a vehicle ( 70 ), where the vehicle ( 70 ) defines a longitudinal axis (x), a transverse axis (y) and a vertical axis (z), wherein the vertical axis (z) is parallel to a gravitational acceleration vector (g) and the sensor unit ( 50 ) comprises at least one acceleration sensor, the acceleration sensor having a predetermined alignment with the vertical axis (z) and configured to output sensor signals for a first acceleration axis (a1) and a second acceleration axis (a2) other than the vertical axis (z) characterized by - detecting (S210) a second sensor signal of the acceleration sensor in response to a linear acceleration of the vehicle ( 70 ) along the longitudinal axis (x); and - determining (S220) the orientation of the sensor unit in a plane spanned by the longitudinal axis (x) and the transverse axis (y) based on the detected second sensor signal. Method according to one of claims 2 to 4, characterized in that the step (S130; 220 ) of determining further comprises - determining, from the second sensor signal, a third angle (ψ) about the third acceleration axis (a3), the third angle (ψ) defining an associated rotation representing the linear acceleration of the vehicle ( 70 ) rotates parallel or antiparallel to the first acceleration axis (a1); and - storing the compensation rotation defined by the third angle (ψ) to enable a transformation so that sensor signals of the acceleration sensor ( 50 ) at accelerations along the longitudinal axis (x) of the vehicle ( 70 ) indicate only one acceleration along the first acceleration axis (a1). Method according to one of the preceding claims, wherein the vehicle ( 70 ) another sensor ( 80 ), which detects a rotation of at least one vehicle wheel directly or indirectly, characterized in that the further steps of: - determining an acceleration value of the vehicle ( 70 ) by detecting sensor signals from the further sensor ( 80 ); Determining an amount of linear acceleration based on the second sensor signal; and determining a deviation of the acceleration value from the amount of the linear acceleration and taking into account the deviation in the step (S130; 220 ) of determining the orientation. Method according to one of the preceding claims, characterized in that it further comprises the following step: issuing a warning if the determined orientation of the sensor unit ( 50 ) signals a faulty installation. Method according to one of the preceding claims, characterized in that the method during a straight travel of the vehicle ( 70 ) is performed. A computer program product having a computer program stored thereon configured to perform a method according to any one of claims 1 to 8 when running on a processor. Contraption ( 300 ) for determining an orientation of a sensor unit ( 50 ), wherein the sensor unit ( 50 ) has at least one acceleration sensor and in a vehicle ( 70 ), characterized by - a registration unit ( 310 ) for detecting a first sensor signal from the acceleration sensor in an acceleration-free state of the vehicle ( 70 ) and / or a second sensor signal from the acceleration sensor in response to a linear acceleration of the vehicle ( 70 ); and a processing unit ( 320 ) for determining the orientation of the sensor unit relative to the vehicle ( 70 ) based on the first sensor signal and / or the second sensor signal. Contraption ( 300 ) according to claim 10, wherein the vehicle ( 70 ) has an Electronic Stability Program (ESP), characterized in that the acceleration sensor ( 50 ) is a three-axis acceleration sensor having a predetermined position to the ESP, so that the determined orientation of the sensor unit ( 50 ) also indicates the orientation of the ESP. Contraption ( 300 ) according to claim 10 or claim 11, characterized in that the acceleration sensor ( 50 ) is integrated in the ESP. Vehicle ( 70 ) with a sensor unit ( 50 ), which has at least one acceleration sensor, characterized by a device ( 300 ) according to any one of claims 10 to 12.

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